有限差分法利用网格节点的差分公式取代控制方程中的各阶导数，然后利用迭代方法求解差分方程，该方法简单、直观且易于掌握。
FDM replace the derivative in control equation with difference formula, and then solve the equation with iterative method, which is simple, intuitionistic and easy to master.
该计划被经济危机所取代，英国机场管理局和英国航空公司对希思罗机场进行了大量投资，这两家公司的严格控制阻碍了希思罗机场的复兴。
The scheme was overtaken by the economic crisis, and the stranglehold of BAA and BA, both of which have a lot invested in Heathrow, has prevented its revival.
法规应该透明简洁，经过严格的成本效益测试，并且以最广泛的以市场为基础的激励取代命令与控制。
Regulations should be transparent and simple, pass rigorous cost-benefit tests, and rely to a maximum extent on market-based incentives instead of command and control.
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